For Musser vibes, like the M 48 Traveler model:

If you take the hook that is attached to the top of the pedal rod, bend it a little more, and "hook" it on the eye hook of the muffle bar, the pedal should stay on a little better.

Hopefully you can download and see the picture I included. It may or may not be clear enough to understand.

/Users/richardpeters/Desktop/IMG_0638.jpeg